name: python-testing description: Helps write pytest tests for Python code including Azure Functions, MCP tools, and API endpoints. Use this skill when creating unit tests, integration tests, fixtures, or mocking external services.

Python Testing Skill

Overview

This skill helps you write comprehensive tests using pytest for Azure Functions, MCP tools, and general Python code.

Project Test Structure

tests/
├── __init__.py
├── conftest.py              # Shared fixtures
├── test_azure_functions.py  # Azure Functions tests
├── test_logic_apps.py       # Logic Apps tests
├── test_mcp_tools.py        # MCP tool tests
└── integration/
    └── test_e2e.py          # End-to-end tests

Writing Tests

Basic Test Pattern

import pytest
from src.abstractions.azure_functions import analyze_data

def test_analyze_data_with_valid_input():
    """Test analyze_data returns correct statistics."""
    result = analyze_data([1, 2, 3, 4, 5])
    
    assert result["count"] == 5
    assert result["sum"] == 15
    assert result["mean"] == 3.0
    assert result["min"] == 1
    assert result["max"] == 5

def test_analyze_data_with_empty_list():
    """Test analyze_data handles empty input."""
    with pytest.raises(ValueError, match="No values provided"):
        analyze_data([])

Testing MCP Tools

import json
import pytest

def test_mcp_analyze_data_tool():
    """Test the MCP analyze_data tool."""
    from src.tool_registry.mcps.src.function_app import analyze_data
    
    # Simulate MCP context (how Azure Functions passes data)
    context = json.dumps({
        "arguments": {
            "values": "[10, 20, 30]"
        }
    })
    
    result = json.loads(analyze_data(context))
    
    assert result["count"] == 3
    assert result["mean"] == 20.0
    assert result["status"] != "error"

def test_mcp_tool_handles_invalid_json():
    """Test MCP tool handles malformed input gracefully."""
    context = json.dumps({
        "arguments": {
            "values": "not valid json"
        }
    })
    
    result = json.loads(analyze_data(context))
    assert "error" in result

Fixtures (conftest.py)

import pytest
from pathlib import Path

@pytest.fixture
def sample_numbers():
    """Provide sample data for tests."""
    return [10, 20, 30, 40, 50]

@pytest.fixture
def mcp_context():
    """Create a factory for MCP context objects."""
    def _create_context(arguments: dict):
        return json.dumps({"arguments": arguments})
    return _create_context

@pytest.fixture
def temp_config_dir(tmp_path):
    """Create a temporary directory with config files."""
    config_dir = tmp_path / "config"
    config_dir.mkdir()
    return config_dir

@pytest.fixture(scope="session")
def azure_function_app():
    """Session-scoped fixture for expensive setup."""
    # Setup that runs once per test session
    app = create_test_app()
    yield app
    # Teardown
    app.cleanup()

Mocking External Services

from unittest.mock import Mock, patch, MagicMock
import pytest

@patch("src.abstractions.azure_functions.requests.post")
def test_function_calls_external_api(mock_post):
    """Test that function calls external API correctly."""
    # Arrange
    mock_post.return_value = Mock(
        status_code=200,
        json=lambda: {"result": "success"}
    )
    
    # Act
    result = call_external_api("test-data")
    
    # Assert
    mock_post.assert_called_once()
    assert result["status"] == "success"

@patch.dict("os.environ", {"API_KEY": "test-key"})
def test_function_uses_env_variable():
    """Test function reads environment variables."""
    result = get_api_key()
    assert result == "test-key"

Parametrized Tests

import pytest

@pytest.mark.parametrize("input_values,expected_mean", [
    ([1, 2, 3], 2.0),
    ([10, 20], 15.0),
    ([100], 100.0),
    ([-5, 5], 0.0),
])
def test_analyze_data_mean_calculation(input_values, expected_mean):
    """Test mean calculation with various inputs."""
    result = analyze_data(input_values)
    assert result["mean"] == expected_mean

@pytest.mark.parametrize("invalid_input,error_message", [
    ([], "No values provided"),
    (None, "Invalid input type"),
    ("not a list", "Expected list"),
])
def test_analyze_data_error_cases(invalid_input, error_message):
    """Test error handling for invalid inputs."""
    with pytest.raises(ValueError, match=error_message):
        analyze_data(invalid_input)

Running Tests

# Run all tests
pytest

# Run with verbose output
pytest -v

# Run specific test file
pytest tests/test_azure_functions.py

# Run tests matching pattern
pytest -k "test_analyze"

# Run with coverage
pytest --cov=src --cov-report=html

# Run only fast tests (skip slow/integration)
pytest -m "not slow"

Test Markers

import pytest

@pytest.mark.slow
def test_large_data_processing():
    """This test takes a while."""
    pass

@pytest.mark.integration
def test_azure_connection():
    """Requires actual Azure connection."""
    pass

@pytest.mark.skip(reason="Feature not implemented yet")
def test_future_feature():
    pass

@pytest.mark.skipif(
    condition=not os.environ.get("AZURE_KEY"),
    reason="Requires AZURE_KEY environment variable"
)
def test_with_azure_credentials():
    pass

pytest.ini Configuration

[pytest]
testpaths = tests
python_files = test_*.py
python_functions = test_*
markers =
    slow: marks tests as slow
    integration: marks tests requiring external services
addopts = -v --tb=short